Abstract 2835: Breast tumor microbiota populations are modulated by chemotherapy and may be indicative of outcome

Abstract

Breast tumors were identified to have their own microbiota population distinct from mammary gland tissue. Breast cancer patients that present in the clinic with larger tumors often undergo neo-adjuvant chemotherapy to reduce tumor burden before surgery. The purpose of our study was to evaluate whether chemotherapy can modulate the tumor microbiome and the potential impact of microbes in the development of distant metastases. Using snap-frozen aseptically collected breast tumor tissue from women that underwent neo-adjuvant chemotherapy or women with no prior therapy at time of surgery, we performed 16S rRNA sequencing to identify tumoral bacterial populations. We also stained breast tumor microarrays (normal breast tissue, primary breast tumor, and lymph node metastases) to confirm presence of identified microbiota. Our data indicates that chemotherapy administration significantly increased breast tumor Pseudomonas and reduced the proportional abundance of Streptococcus. Primary breast tumors from patients that developed distant metastases later on in life (regardless of therapy) displayed increased tumoral abundance of Acinetobacter, Brevundimonas, and Staphylococcus. Stratifying patients based upon BMI indicates that obesity modulates breast tumor microbiota populations and needs to be considered in analyses. Furthermore, we confirm presence of Pseudomonas in breast tumor tissue by immunohistochemical staining. Our results indicate breast tumor microbiota populations can be modified by chemotherapy and specific microbes correlate with tumor recurrence. Further studies with a larger patient cohort may provide greater insights into the role of microbiota in therapeutic outcome and for the development of novel bacterial biomarkers that could predict distant metastases. Citation Format: Akiko Chiba, Alaa Bawaneh, Christine Velazquez, Edward Levine, Katherine L. Cook. Breast tumor microbiota populations are modulated by chemotherapy and may be indicative of outcome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2835.